It is known that the various types of discharge lamps commonly referred to as compact fluorescent lamps, have discharge tubes containing electrodes, filled with a fill gas and sealed in a gas-tight manner, to which discharge tube a cap part being in connection with a power source and suitable for being inserted into a socket, is connected at one or both ends of the discharge tube. In case of single-ended plug-in compact discharge lamps provided with a separate operating unit (e.g., an adaptor type compact fluorescent lamp having a separate ballast circuit and housing arrangement), the cap part consists of a support shell and a closing member fixed to the shell which together, fixed to each other by their rims, make a housing. The shell serves for fixing and supporting the parallel discharge tube legs that are preferably still connected with each other to have the same inner space, the discharge tube legs protrude into the inside of the housing through the openings formed in the base plate. The discharge tube legs extend into the housing but do not reach the base plate of a closing member. The contact members protrude outwardly from the base plate of the closing member and are fixed in the housing, preferably in the base plate of the closing member. The contact members are connected to the electrodes of the discharge tube by means of electrically conducting wires inside the housing.
Fixing the discharge lamp in the socket is ensured by a bossage in the closing member of the cap part, which bossage snaps into a seat formed in the socket for this purpose when the lamp is inserted into the socket. In this instance, the socket referred to is the socket formed in the lower housing member; that is, the discharge lamp of the present invention is configured in the form of an adaptor type of lamp product. The bossage can be placed in the socket also, forming a part of it, but in this case the closing member has to be provided with a seat which the bossage of the socket snaps in.
A disadvantage of the discharge lamp construction described here is that when the cap part is inserted into the socket and particularly when, for disconnection, is pulled out from it, a very great force (load) can be exerted on the mechanical joint between the shell and the closing member. The closing member of the cap part is exposed to critical loads primarily in pulling out the cap part from the socket so that the cap part is gripped at the shell or the discharge tube (so, indirectly at the shell) since to remove the bossage previously snapped into the seat, a rather great force has to be exerted, which is transferred directly to the closing member. It is a further problem that if the contact members (pins) protrude from the closing member there is an increase in the length of the discharge lamp on one part and on the other, the contact members can be easily damaged. The risk of damage is especially high when the user of the discharge lamp is attempting to disconnect it from the socket. The reason for this is that the contact members are in general not guided to fit into the sleeves in the socket formed to accept them and so when the discharge lamp is inserted into the socket by the user, the contact members usually do not fit at once into the sleeves formed to accept them and the user has to turn the discharge lamp back and forth until the contact members find their sleeves and during this process, the contact members can bend or become damaged.